/* ── Reset & variables ─────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:          #0d1117;
  --bg2:         #161b22;
  --bg3:         #1c2128;
  --bg4:         #21262d;
  --border:      #30363d;
  --border2:     #3d444d;
  --text:        #e6edf3;
  --text2:       #8b949e;
  --text3:       #6e7681;
  --accent:      #58a6ff;
  --accent-hover:#79c0ff;
  --green:       #3fb950;
  --green-bg:    #0d2f1a;
  --red:         #f85149;
  --red-bg:      #2a0a0a;
  --yellow:      #d29922;
  --purple:      #bc8cff;
  --sidebar-w:   260px;
  --theory-nav-w:220px;
  --topbar-h:    48px;
  --radius:      8px;
  --radius-sm:   5px;
  --font-mono:   'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
  --font-sans:   -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
  --shadow:      0 4px 16px rgba(0,0,0,.5);
  --transition:  0.15s ease;
}

:root { --footer-h: 36px; }
html, body { height: 100%; font-family: var(--font-sans); background: var(--bg); color: var(--text); overflow: hidden; }

a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent-hover); }
code { font-family: var(--font-mono); font-size: .85em; background: var(--bg4); padding: 1px 5px; border-radius: 3px; color: var(--purple); }
pre { font-family: var(--font-mono); font-size: .82em; background: var(--bg3); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 12px 14px; overflow-x: auto; color: #cdd9e5; line-height: 1.55; }
pre code { background: none; padding: 0; color: inherit; font-size: inherit; }
.hidden { display: none !important; }

/* ══════════════════════════════════════════════
   PRACTICE SECTION
══════════════════════════════════════════════ */
#practice-section {
  display: flex;
  height: calc(100vh - var(--footer-h));
  width: 100%;
  overflow: hidden;
}

/* ── Sidebar ─────────────────────────────────────────────────────────────── */
#sidebar {
  width: var(--sidebar-w);
  min-width: var(--sidebar-w);
  background: var(--bg2);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  height: calc(100vh - var(--footer-h));
  overflow: hidden;
}

#practice-main {
  flex: 1;
  height: 100vh;
  overflow-y: auto;
}

/* ── Sidebar header ──────────────────────────────────────────────────────── */
#sidebar-header {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 16px 16px 12px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}
.logo-icon { font-size: 1.3rem; }
.logo-text { font-weight: 700; font-size: 1rem; color: var(--text); letter-spacing: .3px; }

#sidebar-search-wrap { padding: 10px 12px; flex-shrink: 0; }
#sidebar-search {
  width: 100%;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 6px 10px;
  color: var(--text);
  font-size: .82rem;
  outline: none;
}
#sidebar-search:focus { border-color: var(--accent); }
#sidebar-search::placeholder { color: var(--text3); }

/* ── Nav ─────────────────────────────────────────────────────────────────── */
#sidebar-nav { flex: 1; overflow-y: auto; padding: 4px 0 8px; }
#sidebar-nav::-webkit-scrollbar { width: 4px; }
#sidebar-nav::-webkit-scrollbar-thumb { background: var(--border2); border-radius: 2px; }

.nav-section-header {
  padding: 8px 14px 4px;
  font-size: .68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .8px;
  color: var(--text3);
}

.nav-category {
  padding: 5px 14px 4px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: .82rem;
  color: var(--text2);
  border-left: 2px solid transparent;
  transition: background var(--transition), color var(--transition);
  user-select: none;
}
.nav-category:hover { background: var(--bg3); color: var(--text); }
.nav-category.open { color: var(--text); }
.nav-category .caret { font-size: .7rem; transition: transform var(--transition); }
.nav-category.open .caret { transform: rotate(90deg); }
.nav-category .cat-count { margin-left: auto; font-size: .7rem; background: var(--bg4); color: var(--text3); padding: 1px 6px; border-radius: 8px; }

.nav-question-list { display: none; }
.nav-question-list.open { display: block; }

.nav-question {
  padding: 4px 14px 4px 30px;
  font-size: .79rem;
  color: var(--text2);
  cursor: pointer;
  border-left: 2px solid transparent;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: background var(--transition), color var(--transition);
}
.nav-question:hover { background: var(--bg3); color: var(--text); }
.nav-question.active { background: #1a2f4a; color: var(--accent); border-left-color: var(--accent); }
.nav-question .q-num { font-size: .7rem; color: var(--text3); min-width: 20px; }
.nav-question .q-title { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

.nav-theory-btn {
  margin: 6px 12px;
  padding: 8px 14px;
  background: #2a1f4a;
  border: 1px solid #4a3a7a;
  border-radius: var(--radius-sm);
  color: var(--purple);
  font-size: .82rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: background var(--transition);
}
.nav-theory-btn:hover { background: #3a2f5a; }

.nav-tables-btn {
  margin: 4px 12px 8px;
  padding: 7px 14px;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text2);
  font-size: .82rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: background var(--transition);
}
.nav-tables-btn:hover { background: var(--bg4); color: var(--text); }

#sidebar-footer {
  padding: 8px 14px;
  border-top: 1px solid var(--border);
  font-size: .72rem;
  color: var(--text3);
  flex-shrink: 0;
}

/* ── Practice views ──────────────────────────────────────────────────────── */
.pview { display: none; }
.pview.active { display: block; }

/* ── Home ────────────────────────────────────────────────────────────────── */
#view-home { padding: 32px 36px; }
.home-hero { max-width: 780px; }
.home-hero h1 { font-size: 2rem; font-weight: 700; margin-bottom: 6px; }
.home-sub { color: var(--text2); font-size: 1rem; margin-bottom: 32px; }

.home-cards { display: flex; gap: 16px; flex-wrap: wrap; margin-bottom: 40px; }
.home-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 22px;
  cursor: pointer;
  width: 200px;
  transition: border-color var(--transition), transform var(--transition);
}
.home-card:hover { border-color: var(--accent); transform: translateY(-2px); }
.card-icon { font-size: 1.6rem; margin-bottom: 8px; }
.card-label { font-weight: 600; font-size: .95rem; margin-bottom: 4px; }
.card-desc { font-size: .78rem; color: var(--text2); }

.home-db-info h3 { font-size: .95rem; color: var(--text2); margin-bottom: 10px; font-weight: 600; }
.schema-pills { display: flex; flex-wrap: wrap; gap: 8px; }
.schema-pill {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 4px 12px;
  font-size: .8rem;
  font-family: var(--font-mono);
  color: var(--green);
  cursor: pointer;
  transition: border-color var(--transition);
}
.schema-pill:hover { border-color: var(--green); background: var(--green-bg); }


/* ── Question view ───────────────────────────────────────────────────────── */
#view-question {
  padding: 24px 32px;
  display: none;
  flex-direction: column;
  gap: 0;
  max-width: 1000px;
}
#view-question.active { display: flex; }

#question-header { margin-bottom: 20px; }
#question-meta { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; }
#question-category-badge {
  font-size: .72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: .6px;
  background: #1a2f4a;
  color: var(--accent);
  padding: 2px 8px;
  border-radius: 20px;
}
#question-number { font-size: .8rem; color: var(--text3); }
#question-title { font-size: 1.25rem; font-weight: 700; margin-bottom: 10px; }
#question-description { color: var(--text2); font-size: .92rem; line-height: 1.6; margin-bottom: 12px; }

#question-tables { font-size: .8rem; color: var(--text3); display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.tables-label { font-weight: 600; }
.table-badge {
  background: var(--bg4);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 2px 8px;
  font-family: var(--font-mono);
  font-size: .77rem;
  color: var(--green);
  cursor: pointer;
}
.table-badge:hover { border-color: var(--green); background: var(--green-bg); }

/* ── Editor ──────────────────────────────────────────────────────────────── */
#editor-wrap {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  margin-bottom: 12px;
}
#editor-toolbar {
  background: var(--bg3);
  border-bottom: 1px solid var(--border);
  padding: 6px 14px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.editor-label { font-size: .75rem; font-weight: 600; color: var(--text3); text-transform: uppercase; letter-spacing: .5px; }
.editor-shortcuts { font-size: .72rem; color: var(--text3); }

.CodeMirror { height: 180px; font-family: var(--font-mono); font-size: 13.5px; line-height: 1.6; }

/* ── Action bar ──────────────────────────────────────────────────────────── */
#action-bar { display: flex; gap: 10px; margin-bottom: 20px; }
.btn {
  padding: 7px 18px;
  border: none;
  border-radius: var(--radius-sm);
  font-size: .84rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: background var(--transition), opacity var(--transition);
}
.btn:disabled { opacity: .5; cursor: not-allowed; }
.btn-primary { background: var(--accent); color: #0d1117; }
.btn-primary:hover:not(:disabled) { background: var(--accent-hover); }
.btn-secondary { background: var(--bg3); color: var(--text); border: 1px solid var(--border); }
.btn-secondary:hover:not(:disabled) { background: var(--bg4); border-color: var(--accent); color: var(--accent); }
.btn-ghost { background: transparent; color: var(--text2); border: 1px solid var(--border); }
.btn-ghost:hover:not(:disabled) { background: var(--bg3); color: var(--text); }
.btn-icon { background: none; border: none; color: var(--text2); cursor: pointer; font-size: 1rem; padding: 2px 6px; border-radius: 3px; }
.btn-icon:hover { color: var(--text); background: var(--bg4); }
.btn-copy { background: var(--bg4); border: 1px solid var(--border); color: var(--text2); font-size: .72rem; padding: 2px 8px; border-radius: 3px; cursor: pointer; }
.btn-copy:hover { border-color: var(--accent); color: var(--accent); }

/* ── Results ─────────────────────────────────────────────────────────────── */
#results-panel { border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; margin-bottom: 20px; }
#results-header {
  background: var(--bg3);
  border-bottom: 1px solid var(--border);
  padding: 7px 14px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
#results-label { font-size: .75rem; font-weight: 600; color: var(--text3); text-transform: uppercase; letter-spacing: .5px; }
#results-count { font-size: .75rem; color: var(--green); font-weight: 600; }
#results-body { padding: 0; min-height: 60px; max-height: 280px; overflow: auto; }

.placeholder-msg { padding: 24px 16px; color: var(--text3); font-size: .85rem; text-align: center; }
.error-msg { padding: 12px 16px; color: var(--red); background: var(--red-bg); font-size: .82rem; font-family: var(--font-mono); white-space: pre-wrap; border-top: 1px solid #5c1a1a; }

#results-table-wrap { overflow-x: auto; }
#results-table { width: 100%; border-collapse: collapse; font-size: .82rem; }
#results-table th {
  background: var(--bg3);
  color: var(--text2);
  padding: 7px 12px;
  text-align: left;
  font-size: .75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: .4px;
  border-bottom: 1px solid var(--border);
  white-space: nowrap;
  position: sticky;
  top: 0;
}
#results-table td { padding: 6px 12px; border-bottom: 1px solid var(--border); color: var(--text); white-space: nowrap; max-width: 260px; overflow: hidden; text-overflow: ellipsis; }
#results-table tr:last-child td { border-bottom: none; }
#results-table tr:hover td { background: var(--bg3); }
#results-table td.null-val { color: var(--text3); font-style: italic; }

/* ── Solution ────────────────────────────────────────────────────────────── */
#solution-panel { border: 1px solid #2d4a6e; border-radius: var(--radius); overflow: hidden; margin-bottom: 20px; background: #0e1c2e; }
.solution-header { background: #1a2f4a; padding: 8px 14px; display: flex; justify-content: space-between; align-items: center; font-size: .8rem; font-weight: 700; color: var(--accent); border-bottom: 1px solid #2d4a6e; }
.solution-sub-header { padding: 8px 14px 4px; font-size: .72rem; font-weight: 700; color: var(--text3); text-transform: uppercase; letter-spacing: .5px; display: flex; align-items: center; gap: 10px; }
#solution-sql-display { margin: 0 14px 12px; background: var(--bg3); }
#solution-explanation { padding: 4px 14px 16px; font-size: .87rem; line-height: 1.65; color: var(--text); }
#solution-explanation h3 { font-size: .9rem; margin: 14px 0 6px; color: var(--accent); }
#solution-explanation h4 { font-size: .82rem; margin: 10px 0 4px; color: var(--text2); }
#solution-explanation ul, #solution-explanation ol { padding-left: 20px; margin: 6px 0; }
#solution-explanation li { margin: 4px 0; }
#solution-explanation p { margin: 6px 0; }
#solution-explanation table { border-collapse: collapse; font-size: .8rem; margin: 8px 0; }
#solution-explanation th { background: var(--bg4); padding: 5px 10px; border: 1px solid var(--border); font-weight: 600; color: var(--text2); }
#solution-explanation td { padding: 4px 10px; border: 1px solid var(--border); }

/* ── Table browser (practice) ────────────────────────────────────────────── */
#view-tables { padding: 32px 36px; }
.page-header { margin-bottom: 28px; }
.page-header h2 { font-size: 1.4rem; font-weight: 700; margin-bottom: 6px; }
.page-header p { color: var(--text2); font-size: .9rem; }

.tab-bar { display: flex; gap: 4px; margin-bottom: 20px; border-bottom: 1px solid var(--border); }
.tab-btn { padding: 7px 16px; background: none; border: none; color: var(--text2); cursor: pointer; font-size: .85rem; border-bottom: 2px solid transparent; margin-bottom: -1px; font-family: var(--font-mono); transition: color var(--transition), border-color var(--transition); }
.tab-btn:hover { color: var(--text); }
.tab-btn.active { color: var(--green); border-bottom-color: var(--green); }

.table-panel { display: none; }
.table-panel.active { display: block; }

.schema-table { border-collapse: collapse; font-size: .82rem; width: 100%; margin-bottom: 24px; }
.schema-table th { background: var(--bg3); padding: 7px 12px; border: 1px solid var(--border); font-weight: 600; color: var(--text2); text-align: left; }
.schema-table td { padding: 6px 12px; border: 1px solid var(--border); color: var(--text); font-family: var(--font-mono); font-size: .8rem; }
.schema-table tr:nth-child(even) td { background: #13181e; }
.type-tag { color: var(--yellow); }
.pk-tag { background: #2d1b5a; color: var(--purple); font-size: .7rem; padding: 1px 5px; border-radius: 3px; }
.fk-tag { background: var(--green-bg); color: var(--green); font-size: .7rem; padding: 1px 5px; border-radius: 3px; }
.sample-section h4 { font-size: .8rem; color: var(--text3); text-transform: uppercase; letter-spacing: .5px; margin: 0 0 10px; font-weight: 600; }


/* ══════════════════════════════════════════════
   THEORY SECTION  (full-screen takeover)
══════════════════════════════════════════════ */
#theory-section {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: var(--footer-h);
  z-index: 500;
  background: var(--bg);
  display: flex;
  flex-direction: column;
}

#theory-topbar {
  height: var(--topbar-h);
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 0 20px;
  flex-shrink: 0;
}

#btn-back-to-practice {
  background: var(--bg3);
  border: 1px solid var(--border);
  color: var(--text2);
  padding: 5px 14px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: .82rem;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: border-color var(--transition), color var(--transition);
  white-space: nowrap;
}
#btn-back-to-practice:hover { border-color: var(--accent); color: var(--accent); }

#theory-topbar-title {
  font-weight: 700;
  font-size: .95rem;
  color: var(--purple);
}

#theory-body {
  display: flex;
  flex: 1;
  overflow: hidden;
}

/* ── Theory left nav ─────────────────────────────────────────────────────── */
#theory-nav {
  width: var(--theory-nav-w);
  min-width: var(--theory-nav-w);
  background: var(--bg2);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  padding: 12px 0;
}
#theory-nav::-webkit-scrollbar { width: 4px; }
#theory-nav::-webkit-scrollbar-thumb { background: var(--border2); border-radius: 2px; }

.theory-nav-header {
  padding: 4px 16px 8px;
  font-size: .68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .8px;
  color: var(--text3);
}

.theory-nav-item {
  padding: 9px 16px;
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  font-size: .85rem;
  color: var(--text2);
  border-left: 2px solid transparent;
  transition: background var(--transition), color var(--transition);
}
.theory-nav-item:hover { background: var(--bg3); color: var(--text); }
.theory-nav-item.active { background: #2a1f4a; color: var(--purple); border-left-color: var(--purple); }
.theory-nav-item .tn-icon { font-size: 1rem; }

/* ── Theory content area ─────────────────────────────────────────────────── */
#theory-content-area {
  flex: 1;
  overflow-y: auto;
  padding: 36px 44px;
}
#theory-content-area::-webkit-scrollbar { width: 7px; }
#theory-content-area::-webkit-scrollbar-thumb { background: var(--border2); border-radius: 4px; }

#theory-home-panel h2 { font-size: 1.5rem; font-weight: 700; margin-bottom: 6px; }
#theory-home-panel > p { color: var(--text2); font-size: .9rem; margin-bottom: 28px; }

#theory-cards-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 16px; }
.theory-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  cursor: pointer;
  transition: border-color var(--transition), transform var(--transition);
}
.theory-card:hover { border-color: var(--purple); transform: translateY(-2px); }
.theory-card-icon { font-size: 1.8rem; margin-bottom: 10px; }
.theory-card-title { font-weight: 700; font-size: .95rem; margin-bottom: 6px; }
.theory-card-summary { font-size: .8rem; color: var(--text2); line-height: 1.5; }

/* ── Theory detail ───────────────────────────────────────────────────────── */
.theory-content { max-width: 820px; }
.theory-content h2 { font-size: 1.5rem; font-weight: 700; margin-bottom: 20px; border-bottom: 1px solid var(--border); padding-bottom: 12px; }
.theory-content h3 { font-size: 1rem; font-weight: 700; margin: 22px 0 10px; color: var(--accent); }
.theory-content h4 { font-size: .88rem; font-weight: 600; margin: 14px 0 6px; color: var(--text2); }
.theory-content p { font-size: .9rem; line-height: 1.7; color: var(--text2); margin: 8px 0; }
.theory-content ul, .theory-content ol { padding-left: 22px; margin: 8px 0; }
.theory-content li { font-size: .88rem; line-height: 1.65; color: var(--text2); margin: 4px 0; }
.theory-content table { border-collapse: collapse; font-size: .82rem; margin: 10px 0; width: 100%; }
.theory-content th { background: var(--bg3); padding: 7px 12px; border: 1px solid var(--border); font-weight: 600; color: var(--text2); text-align: left; }
.theory-content td { padding: 6px 12px; border: 1px solid var(--border); color: var(--text); }
.theory-content tr:nth-child(even) td { background: #15191f; }

.theory-box { background: var(--bg2); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px 18px; margin: 12px 0 20px; }
.theory-box p { color: var(--text2); }


/* ══════════════════════════════════════════════
   SHARED COMPONENTS
══════════════════════════════════════════════ */

/* ── Modal ───────────────────────────────────────────────────────────────── */
.modal { position: fixed; inset: 0; z-index: 1000; display: flex; align-items: center; justify-content: center; }
.modal-overlay { position: absolute; inset: 0; background: rgba(0,0,0,.7); }
.modal-box {
  position: relative;
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  width: 90%;
  max-width: 680px;
  max-height: 80vh;
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow);
  overflow: hidden;
}
.modal-header { display: flex; justify-content: space-between; align-items: center; padding: 12px 16px; border-bottom: 1px solid var(--border); font-weight: 700; font-size: .95rem; font-family: var(--font-mono); color: var(--green); }
.modal-tabs { display: flex; border-bottom: 1px solid var(--border); }
.modal-tab { background: none; border: none; padding: 8px 16px; color: var(--text2); cursor: pointer; font-size: .82rem; border-bottom: 2px solid transparent; transition: color var(--transition), border-color var(--transition); }
.modal-tab:hover { color: var(--text); }
.modal-tab.active { color: var(--accent); border-bottom-color: var(--accent); }
.modal-panel { overflow: auto; padding: 16px; flex: 1; }

/* ── Loading overlay ─────────────────────────────────────────────────────── */
#app-loader {
  position: fixed;
  inset: 0;
  background: rgba(13, 17, 23, 0.92);
  z-index: 2000;
  display: flex;
  align-items: center;
  justify-content: center;
}
.loader-box {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 36px 40px;
  text-align: center;
  max-width: 360px;
  box-shadow: var(--shadow);
}
.loader-spinner { width: 28px; height: 28px; border-width: 3px; display: inline-block; margin-bottom: 16px; }
#loader-msg { font-size: .95rem; font-weight: 600; color: var(--text); margin: 0 0 8px; }
.loader-sub { font-size: .78rem; color: var(--text3); line-height: 1.55; margin: 0; }

/* ── Spinner ─────────────────────────────────────────────────────────────── */
.spinner { display: inline-block; width: 14px; height: 14px; border: 2px solid var(--border); border-top-color: var(--accent); border-radius: 50%; animation: spin .6s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }

/* ── Scrollbars ──────────────────────────────────────────────────────────── */
::-webkit-scrollbar { width: 7px; height: 7px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border2); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: #4a545e; }

/* ── Persistent footer ───────────────────────────────────────────────────── */
#app-footer {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: var(--footer-h);
  z-index: 600;
  background: var(--bg2);
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  font-size: .75rem;
  color: var(--text3);
}

.footer-credit-link {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  color: #0a66c2;
  font-weight: 600;
  font-size: .75rem;
  text-decoration: none;
  transition: color var(--transition);
}
.footer-credit-link:hover { color: #1e85d4; }
.footer-credit-link svg { width: 13px; height: 13px; flex-shrink: 0; }

/* ── Responsive ──────────────────────────────────────────────────────────── */
@media (max-width: 700px) {
  #sidebar { display: none; }
  #view-home, #view-tables { padding: 20px 16px; }
  #view-question { padding: 16px; }
  .home-cards { flex-direction: column; }
  .home-card { width: 100%; }
  #theory-nav { display: none; }
  #theory-content-area { padding: 20px 16px; }
}